Klaus Knopper has remarked on the subject that DVD uncompressed is slower due to the I/O of data retreival.

Especially note that DVD .iso is limited to 2GB in media and usually translates to around 5GB of uncompressed format.

Trying to retrieve data from a 5GB store of data is bound to be slower than trying the same from a 2GB store. Decompression is a much faster operation then I/O.

Today's storage systems in pentabytes ...terrabytes... have horrendous problems in trying to retrieve data. Special techniques are required to implement retrieval. Considering this phenomenon may shed some understanding of the problem that uncompressing Knoppix DVD produces in retrieving program data.

Klaus Knopper has produced the fastest Live CD out there and has plans for a DVD version for next release. I eagerly await the release.